Electrical heating unit



SePt- 3 1940- '.1. E. SMITH 2,213,723

ELECTRICAL HEATING UNIT Filed Dec. 3l, 1937 BY v ATTORNEY.

Patented Sept. 3, 1940 UNET it-il'i'hiii'i Application December' 3l, i937, Serial No. 152,713

14 Claims.

This invention relates to electrical heating devices, and more particularly to a heating unit adapted for installation in a heating vessel such as a coiee percolator.

According to one of the features of this invention the unit provided with two heating ele ments, one of which is used in developing the necessary high heat for percolating water through the coffee, whereas the other element is employed for furnishing the required low heat to lreep the prepared coffee at the desired temperature.

Another feature of improvement resides in the provision oi a water well adjacent the heating elements and in communication with the fluid in the heating vessel, the arrangement of the parts being such that the heat generated in the high temperature heating element is rapidly transferred to the fluid in the water well. For this purpose the high temperature element is cast within a housing comprising a body of metal of high thermal conductivity such as aluminum. The heating element is embedded in ceramic insulation and positioned close to the Well so that the intervening thickness of metal therebetween is relatively small. On shrinking, the metal of the casting creates tremendous pressure against the ceramic coverings of the heating element, ther ,Jy setting up compressive and compacting forces thereagainst bringing the parts of the heating element into intimate contact with the metallic housing for the most enicient transfer of heat.

As a result of rapid ltransfer of heat from the ilament, through the body of the metal housing and into the water well, it is possible to work the iilament at a very high wattage and to there- Alore bring the water in the heating vessel to percolating temperature in a relatively short space of time.

Preferably the electrical connections are such that the low heat elemenu remains on continuously, whereas the high heat or percolating element is ccnnected through a suitable switch for turning on or ofi as needed.

Another feature of this invention is the provision of a novel fuse arrangement in the circuit of the high heat element to protect the saine against destructive high temperatures.

Various other :features of advantage will appear as the description proceeds, reference being made to the accompanying drawing in which:

Figure l is a top plan view of heating unit embodying my invention, with the fuse portion broken away in section,

Fig. 2 is a vertical section on the line 2 2 of Fig. l, and

Fig. 3 is a side elevation of the heating unit installed in the bottom of a coiiee percolator, the walls of which are shown broken away in section.

ln the drawing, the reference numeral lil indicates a heating unit comprising a housing El having a water well l2 opening into the interior oi a coffee percolator or other heating vessel The well extends downward within the housing i i and may be reduced in diameter as shown at l5 to extend within the convolutions of a spiral heating element l@ having a ceramic insulating covering il. Preferably, the housing li is formed or metal having high thermal conductivity such as aluminum, and is cast around the spiral heating element it so as to completely enclose the same in the metal surrounding the water well. By reason of the shrinkage of the metal oi the housing in cooling after casting, there is a tremendous pressure exerted by the metal against the surface of the ceramic material il embedding the heating element it. The parts are thereby brought in very close contact under pressure and any resistance to heat transfer from the heating element it to `the metal of the housing is reduced to a minimum. Therefore, the transmission of heat from the heating element to the well is carried out rapidly and with high eniciency. As a further advantage of this construction the heating element l@ can be worked at very high wattage owing to the rapidity oi heat transfer therefrom to the adjacent portions oi the highly conductive metal of the housing.

For convenience in attaching the housing to the heating vessel iii, the latter is provided with an opening i2, and the housing is reduced and threaded at the upper portion surrounding the wel] i2 as indicated at i9 for receiving a nut 2Q adapted to clamp the wall of the vessel i between a shouider 2l of the housing, an interposed washer iii, and the lower face of the nut As 'thus installed, the heating element SG and the well i2 are in position to quickly and eniciently set up the high temperatures required in the heating vessel. Current may be supplied to the heating element le through the medium of terminal pins carried by a bracket and adapted for connection to a service plug (not shown), electrical connections being completed through .a fuse 24, a toggle switch 25, and the wiring connections 25, El and 2E.

There is also provided a warming element at the base of the housing beneath the water well.

Preferably, this is in the form of a member or housing 29 having a circumferential channel 3! containing a heating element Si embedded in ceramic material 32.

A tapered extension E3 at the base of the y housing ii fits a similarly tapered depression 3d in the member 29. A lug 35 at the bottom of the extension 33 passes through an opening 36 of a plate 3i' which covers Ithe ceramic material 32 of the heating element Si, the lug 35 being swaged or riveted over at 3S'. These parts are fastened as a unit to the housing il by means of a threaded stud 39 and a nut lii. The bracket 23 may be secured to the plate 3i by spot welding or in any other approved way.

Current is fed to the heating element 3i from the terminal pins 22 to which the ends All of said element are permanently connected.

If desired, the housing Z9 may be made larger in diameter or have an offset portion to permit the wire to be brought up through the top of the housing and directly to the terminal posts 22, thereby eliminating the insulation ll in the bracket 23.

The fuse arrangement 2li may comprise a pair of spring blades 42 and i3 mounted on a screw threaded stud lili, the blade l2 being connected to the conductor 2l and insulated from the stud lli by insulating washers i5 and i6 and a collar of insulation Lil. The other spring blade i3 is mounted in side-by-side relation to the blade li on the stud lili, and the assemblage of parts is held rmly together by a nut i8 tightened against the outer face of the blade 43. The conductor El engages the spring blade d2 behind the washer i6 and is also insulated from the bracket 23 at the terminal pins 22 by insulating washers 49. Conductor 28 is similarly insulated from the opposite terminal pin by washers Eil. The fuse element comprises a pair of metal pieces 52 bent toward` each at one end and held together by fuse metal 53. The legs of the fuse element engage over the free ends of the spring blades [i2 and d3, holding them toward each other under tension.

If desired, this heating unit maybe fitted with a pump as indicated at 5d having a rising tube portion 55 adapted to hold a percolator screen (not shown).

In operating the heating unit, a service plug is connected to the terminal pins 22, and the toggle switch turned on to permit current to enter the heating element i6. The heat generated by the heating element is rapidly transferred through the highly conductive metal of the housing il and into the well openings l5 and l2, from which it rises into the zone of the pump and thence into the percolator screen by circulation through the pump tube.

Temperature variations in the heating element and the adjacent portions of the low fusing housing are quickly followed by the fuse element, so that it is at all time an eicient gage of thermal conditions in the heating unit, and will act in time to break the circuit before destructive temperatures have been reached in the parts designed to be protected.

The fuse 25 and its holding means, as illustrated in the present example of the invention, have been positioned so as to place the fuse where it will be quickly responsive to temperature changes in the heating unit, but it is to be understood that the construction and location of the fuse element may be changed if found advantageous.

After the contents of the vessel il? have been heated to the proper degree and the percolating operation completed, the heating element 3i being energized at all times through the service plug terminals is capable of keeping the liquid coffee at the proper temperature for serving.

It is to be understood in conclusion that the invention as above exempliiied may be embodied in various other forms of construction and modifications, and is therefore not restricted in its applications except as defined in the appended claims.

I claim:

1. An electrical heating unit adapted for installation in a heating vessel, comprising a housing having a water well communicating with the interior of the vessel, said well being reduced in size adjacent the bottom thereof, a spiral heating coil surrounding the reduced portion of the well, a second heating element beneath said coil at the base of said housing, and a circulating pump mounted at the upper end of the Well and communicating with the interior of the vessel.

2. An electrical heating unit adapted for installation in a heating vessel, comprising a housing having a water well communicating with the interior of the vessel, a heating element ernbedded in insulating material in said housing adjacent the well, a second housing beneath said well, said second housing having a circumferential channel, a heating element embedded in insulating material in said channel, a plate covering the insulating material, and means for holding the two housings together, the second heating element being adapted to supply additional heat to the well directly through the body of the housing.

3. An electrical heating unit adapted for nstallation in a heating vessel, comprising a housing having a water well communicating with the interior of the vessel, a heating element in said housing associated with the well, a second housing having a circumferential channel beneath said well, a heating element in said channel, a plate covering the channel, said second named housing having a lug portion extending through an opening in said plate, the lug being swaged over on the outside of the plate, and fastening means including a threaded part passed through said lug and into the base of the rst named housing.

4. An electrical heating unit, comprising a housing having a water well, said housing being of metal and of high thermal conductivity cast around a heating element associated with the i Well, and a second housing carrying a heating element and detachably connected to the first named housing.

5. An electrical heating unit, comprising a housing having a water well, said housing being of metal of high thermal conductivity cast around a heating element associated with the `Nell, and a second housing having a channel containing a heating element, said second housing being secured to the first named housing beneath the well.

6. An electrical heating unit, comprising a housing having a water well, said housing being of metal of high thermal conductivity cast around a spiral heating element, said well extending downward into the spiral heating element, and a second heating element associated with said housing beneath the Well.

7. An electrical heating unit, comprising a housing having a water well, said housing being of metal of high thermal conductivity cast around a heating element associated with the Well, and a second housing carrying a heating element and detachably connected to the rst named housing, the latter being reduced adjacent the mouth of the well to form a shoulder, the reduced portion extending through an opening in the bottom of a heating vessel, and means for holding said shoulder against the outer portion of the vessel surrounding said opening.

8. An electrical heating unit adapted for installation in a heating vessel, comprising a housing having a water well communicating with the interior of the vessel, a heating element in said housing associated with the Well, a second housing having a circumferential channel beneath said well, a heating element in said channel, a plate covering the channel, and means for securing said plate in place.

9. An electrical heating unit adapted for installaton in a heating vessel, comprising a housing having a water well communicating with the interior of the vessel, a heating element in said housing associated with the well, a second housing having a circumferential channel beneath said well, a heating element in said channel, a plate covering the channel, a mount for a pair of terminals arranged to receive a detachable service plug, and means for securing said plate and said terminal mount to said housing.

10. An electrical heating unit comprising a housing having a water Well, said housing being of metal of high thermal conductivity cast around a heating element adjacent the well, a second heating element of smaller capacity than the rst mentioned heating element and associated with said well, a pair of terminals to which said heating elements are connected, and a fuse connected in circuit between the terminals and the heating element of higher capacity.

11. An electrical heating unit comprising a housing having a water well, said housing being of metal of high thermal conductivity cast around a heating element adjacent the well, and a sec- V ond heating element of smaller capacity than the iirst mentioned heating element and operatively associated with said Well, a pair of terminals to which the heating elements are con- 5 nected, and a switch arranged to interrupt the circuit to one of said heating elements.

12. Means for heating the contents of a vessel comprising an electrical heating unit mounted therein and having a housing with a water well 10 communicating with the interior of the vessel, the well having an area of reduced capacity at its lower end, and a heating coil adjacent the lower end of said Well, and a circulating pump mounted at the upper end of the well having 15 a valve for controlling the ow of water to said Well. 1

13. An electrical heating unit adapted for installation in a heating Vessel, comprising a housing having a water well communicating with the l0 interior of the vessel, a spiral heating coil surrounding the base of said Well, a second heating element surrounding the bottom of the housing beneath the spiral coil, the base of said well comprising a cavity of reduced capacity, and a cir- 25 culating pump mounted at the upper end of the well and communicating with the interior of the vessel.

14. An electrical heating unit adapted for installation in a heating vessel, comprising a hous- 30 ing having a water well communicating with the interior of the vessel, a heating element in said housing surrounding the Well, terminal means associated with said housing adapted for connection to a power line, a fuse between said heating 35 element and said terminal means, and a second heating element beneath the well at the base of the housing, said second element being connected directly to said terminal means, and being of smaller capacity than the rst mentioned 4G heating element.

JOHN E. SMITH. 

